Display screen or portion thereof with a graphical user interface



The FIGURE depicts a front view of a display screen or portion thereof with a graphical user interface showing the new design.

The broken line showing a display screen with graphical user interface is included for the purpose of showing portions of the article that form no part of the claim. The other broken lines in the figure show portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 